The present disclosure relates to an image processing apparatus and an image processing method which detect an object by using an image processing technique based on background subtraction.
In conventional surveillance camera systems, a surveillant checks video taken by a surveillance camera to detect abnormalities. However, with the development of image processing techniques in recent years, there has been an increase in the number of surveillance camera systems which automatically detect objects with surveillance cameras or image processing apparatuses connected to surveillance cameras. Such systems provide alarm displays or alarm notifications by e-mail when abnormalities occur.
Even when an abnormality occurs, the abnormality might not be detected by the surveillance methods in which the surveillant checks the video manually because of carelessness or insufficient surveillance skill. On the other hand, surveillance methods using image processing can make an improvement in the above-described defects and can save manpower, thus they are being increasingly introduced.
One of the methods which automatically detect objects, background subtraction, is widely and generally used. The background subtraction stores a previously-captured background image which does not include an anomaly and extracts the foreground part based on the difference between the current image and the background image.
However, it is sometimes difficult to accurately capture an object because of the location conditions of the surveillance camera, the weather thereof, and the like. Especially when the surveillance camera is installed outdoors, the surveillance camera is influenced by light changes due to weather conditions. Accordingly, it is necessary to capture an object by properly and continuously updating the background image.
While there is a demand for automatic detection of abnormalities through image processing for surveillance camera images as described above, surveillance methods using image processing set off many false alarms due to false detection. Accordingly, there is a need for a method which detects an object with high accuracy.
Especially outdoors, the sun may be blocked by clouds and then come out again, causing quick changes in sunlight in some cases, where the entire image is different from the background image, thus making it difficult to detect an object.
In the light of the aforementioned problem, Japanese Patent Laid-open Publication No. 2000-59669 (Patent Literature 1) discloses an image processing apparatus which updates the background image when optical parameters change.